A hybrid or electric vehicle may include a heat pump for heating and cooling a passenger cabin responsive to a desired passenger cabin temperature. During some conditions where ambient air temperature is low and cabin heating is requested, an exterior heat exchanger may be operated as an evaporator to extract heat from ambient air to heat the passenger cabin. However, humidity in the ambient air may freeze fins of the exterior heat exchanger as air passes over the heat exchanger fins. Further, the exterior heat exchanger may freeze during other conditions, such as if snow becomes impacted in the exterior heat exchanger. If the exterior heat exchanger fins remain in an iced state, passenger cabin heating may be reduced causing passenger discomfort. One way to remove ice from the exterior heat exchanger is to operate the heat pump in a de-icing mode. In de-icing mode, refrigerant is heated via a compressor and passed through the exterior heat exchanger to warm the exterior heat exchanger. However, refrigerant returned to the heat pump compressor may be at a higher temperature than is desired. Consequently, the heat pump's compressor may be degraded if the heat pump is operated in de-icing mode for an extended period of time. Additionally, known de-icing methods do not allow the passenger cabin to be heated while the heat pump is operating in de-icing mode.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating a vehicle heat pump, comprising: receiving vehicle heat pump sensor data to a controller; judging a presence or absence of exterior heat exchanger icing via the controller; and operating the vehicle heat pump in a cooling mode via the controller in response judging the presence of exterior heat exchanger icing.
By operating the vehicle heat pump in a cooling mode in response to a presence of exterior heat exchanger icing, it may be possible to provide the technical result of increasing a rate of exterior heat exchanger de-icing. Further, operating the heat pump in a cooling mode may reduce the possibility of heat pump compressor degradation. For example, a heat pump may at first be operated in a de-icing mode to reduce exterior heat exchanger icing. However, if the de-icing takes longer than is desired, the heat pump may switch from de-icing mode to a cooling mode to continue exterior heat exchanger de-icing since the heat is rejected to the exterior heat exchanger when the heat pump is operated in a cooling mode. In some examples, passenger comfort may be maintained when the heat pump operates in a cooling mode via activating a positive temperature coefficient (PTC) heater while the exterior heat exchanger is being de-iced in the cooling mode. In other examples, if the vehicle includes an engine, the engine may be activated to maintain passenger comfort while the exterior heat exchanger is being de-iced in the cooling mode.
The present description may provide several advantages. For example, the approach may improve heat pump efficiency in heating mode by de-icing the exterior heat exchanger. Additionally, the approach may maintain passenger comfort by using an electric coolant heater to reject air to the passenger cabin at a desired temperature during exterior heat exchanger de-icing. Further, the approach may be applicable to both electric and hybrid vehicles.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.